PROJECT SUMMARY/ABSTRACT CORE A ? ADVANCED PROTEOMICS CORE The goal of Core A is to provide mass spectrometry?based proteomic platforms for global and targeted characterization of transcriptional regulators that play a central role in cardiac development and congenital heart defects in support of the aims and efforts for Projects 1?3 of the proposed PPG Project. We are continuously developing new and innovative strategies for more sensitive and quantitative analysis of protein- protein interactions (PPIs) and post-translational modifications (PTMs). These efforts now allow us to look beyond static PPIs or PTMs and towards more dynamic characterization in the context of different developmental stages, gene knockouts or gene mutations. Our affinity-purification mass spectrometry (AP-MS) capabilities along with newly developed proximity-based biotinylation (APEX-MS), will aid research in Projects 1?3 through dynamic interaction network mapping for transcriptional regulators, such as GATA4, TBX5, MEF2C, Myocardin and BAF complex members. Also, our quantitative analyses pipeline to determine PTMs on specific proteins will provide direct support for researchers in Project 3, focused on MEF2C and Myocardin, two signal responsive factors. All of these experiments will be performed in relevant systems for cardiac development, either induced pluripotent stem cell (iPSC)- or embryonic stem cell (ESC)-derived cardiac precursors (CPs), as well as cardiomyocytes (CMs) or cardiac tissue derived from neonatal mice. Beyond support of the projects, Core A will work closely with Core B to develop analysis strategies for APEX-MS data. The expertise, the highly sensitive and quantitative MS analysis, as well as ongoing innovations provided by Core A will serve and adapt to the needs of Projects and Cores of the PPG project.